Chapter 5

Understanding the Link Profile

Scope

The examples in this chapter were created using the RADWIN OLBC for RADWIN 2000 prod­ucts. Link Profiling is generic, applying equally to RADWIN 5000 HPMPand WinLink 1000 products.

Generating a Link Profile

Suppose for example, you enter the following coordinates and click Set:

gsc_02120.png 

The range will be calculated and displayed:

gsc_02130.png

Note

Recall that you can enter latitude and longitude in degree-minute-second format by typing each coordinate as a space-separated triple like this:

30°12”16’ should be entered as 30 12 16.

If you click View, a new tab or window is opened by your browser with the following display:

gsc_02140.png

 

Figure 5-1: Google Earth plug-in: Terrain display and Link Profile

Oops!

Instead of Figure 5-1, I got this:

gsc_02150.png 

Click the Get the Google Earth Plug-in now button, and follow the instructions. See Appendix B for detailed installation instructions.

In your browser, click either of the sites - say A:

osc_20280.jpg 

Figure 5-2: Google Earth plug-in site display

The display shows the azimuth (compass setting) to the other site (B), the distance and the Fresnel clearance (60%).

You may return to the Coordinates window and click Set to transfer the results to the dis­tance calculation area in the RADWIN OLBC main window. The display of Figure 5-1 remains open.

Note

At this point, Internet Explorer and Mozilla Firefox behave differently:

•         If you make a change to the coordinates and click View, Internet Explorer does nothing unless you closed the previous display. You can change its behavior by manipulating the relevant Internet set­tings.

•         Mozilla Firefox reuses the open tab and updates it immediately

Working with a Link Profile

Suppose that we enter the following coordinates (somewhere in the Sahara Desert):

gsc_02220.png 

Here are the results:

gsc_02230.png 

Here is the Terrain Display and Link Profile from the plug-in:

gsc_02240.png

 

The Link Profile shows the contribution of the terrain and the earth’s curvature to link interfer­ence for the selected antenna height. The latter appears exaggerated due to the choice of vertical scale. The actual contribution of the earth’s curvature over a range of 120 km (74.6 miles) is 255 m (837’). This situation is untenable, so we need to refine the profile.

Refining the Link Profile

Suppose for example we had tall buildings or hills at both link sites, enabling us to set our antennas 320m above ground level:

gsc_02250.png 

The calculation results are as before -

gsc_02260.png 

but this time the link profile is quite different:

gsc_02270.png

 

This time we have LOS, but there is some terrain intrusion into the 60% Fresnel zone. A pos­sible solution would be to split the link into two roughly equal segments, which would also reduce our tower heights to something more realistic than 320m! This takes us into the domain of Link Planning which is beyond the scope of this Guideline. RADWIN supplies a Link Planner to meet this need.

For Further Information about Link Planning

Just below the link profile, there are three Internet links:

•         Print this page

•         Add to Favorites

•         Planning Support

Clicking the Planning Support link opens an email page:

osc_00300.png 

Your Terrain Display and Link Profile are saved on the RADWIN OLBC site as shown. (If you Ctrl-Click the site it will open your link site in Google Earth.)

Feel free to add further comments or questions to the email. A RADWIN Professional Support engineer will contact you by return email as soon as possible.